The Spatial Distribution of Soil Nitrogen Storage and the Factors That Influence It in Central Asia’s Typical Arid and Semiarid Grasslands

Abstract

Using a structural equation model (SEM), this paper investigates the response of soil nitrogen content of five typical grasslands in the middle line countries of China’s “Belt and Road” initiative to the changes of climate variables, soil pH value, and normalized vegetation index, and employs the principal component analysis method to determine the spatial variation characteristics and influencing factors of nitrogen reserves in different grasslands. Pontiac grassland (PS), Middle East grassland (MES), Kazakh grassland (KS), Kazakh forest grassland (KFS), and Kazakh semi-desert grassland (KFS) are the five grasslands in the research region (KSD). The results indicated that (1) the nitrogen reserves of the five grassland soils (0–100 cm) in the research area were 7.49 Pg, or approximately 5.7 percent of the total world nitrogen reserves. The sum of the five grasslands’ 0–30 cm and 0–50 cm N reserves accounted for 36.3 percent and 63.1 percent, respectively, of the total 0–100 cm N reserves. The density of nitrogen in the soil (0–100 cm) varied significantly between grasslands, ranging from 1.47 to 3.87 kg/m2, with an average of 3.10 kg/m2. (2) PCA analysis revealed a substantial positive correlation between soil N and MAP (p p 2 value was 0.08, indicating an average fit.

Keywords

• arid–semiarid grasslands
• spatial distribution of nitrogen stocks
• principal component analysis
• environmental factors
• structural equation modeling